Apparatus for the measurement of the relative axial displacement of a rotor and a stator



l June 242, 1965 R. G. HoLz APPARATUS FOR THE MEASUREMENT 0F THE RELATIVE AXIAL I DISPLACEKENT OF A ROTOR AND A STATOR Filed'Dct. 27. 1961 num/e1;

3,190,125 APPARATUS FOR `THE MEASUREMENT OF THE RELATIVE AXIAL DISPLACEMENT 0F A ROTOR Robert Gustave Holz, Draveil, Seine ct Oise, France, ar signor to Societe Nationale dEtude et de Construction de Moteurs dAviation, Paris, France, a company of France Filed Oct. 27, 1961, Ser. No. 148,121

Nov. 7, v1960,

Claims priority, application France,

8 6 3 Claims. (CI. 73-432) The adaptation of the aviation turbo-reactor to ight at very high speeds has resulted in the progressive elimination of light alloys for the moving parts, by reason of the creepv considerations of weight, light alloys have been retained as far as possible for the fixed parts. This results in considerable differences in expansion necessitating an increase in the clearances, which is always disadvantageous from the performance point of view.

lt is, however, important to have an exact knowledge of the variation of the clearances depending on the stateand the conditions of operation, in order to determine the dimensions precisely.

The present invention makes it possible to measure in' stantancously thc relative axial displacement between the rotor and the stator of a turbine, especially of a gas turbine, such measurement being particularly difficult in view ofthe very exacting conditions of temperature and of vibration.

In accordance with the present invention, the passage of a rotor blade is detected on the one hand in front of a straight reference line parallel to the axis of rotation, and on theothcr hand in front of a line inclined to the said reference line, and the time taken for the blade to pass between these two lines is measured.

The present invention has also for its object an electronic device for carrying this method into effect, which device comprises an electrode mounted on the stator of the machine facing the rotating blades and constituted by at least ene rectilinear branch parallel to the axis of rotation and a second branch preferably be 45.

in order to simplify the design of the electronic circuit, the present invention provides for the connection to earth facilitated by kinetic heating, whereas, for

of the rotating electrode through the intermediary of the? rotor bearings. t c" n A The description which f awr. below with reference to the accompanying drawrlgsy (which are given by way of example only and not in any limitative sense), will make4 it qui e clear how the invention can be carried into effect, the :pccial features wh'cn are brought out either in the text or in the drawings of the said invention.

Flt. 1 is a perspective view of the-turbine with part being understood'v to form a part 'ou'scalibratom g position ofthe rotation at any ins-taut can Patented June 22, 1965 by a connection diagram of the measuring circuit. FIG. 2 ls a View of the oscilloscope screen.

the periphery of one blade 4 of the rotor.

The moving electrode 3 is connected to earth through the intermediary of the bearings of the mtor shaft, while under tension by connecting electric circuit: three impulses for each complete revo lutron ofthe rotor` These impulses of rounded shape, as shown at 8, are collecteo at a p omt 9 ot the circuit, applied to an arnconstant over the rotor, is reduced r'owcr to produce on the screen i justtng the oscilloscope, three lines 17 will be caused to appear on tac Screen, as shown in FIG. 2, the position ot cach line corresponding to a detinite instant.

The device which has just been described operates in the tollowing manner:

During a relative loscope will remain fixed, on the condition of course that the speed of rotatiot is constant (these two lines will approach cach other in the event of acceleration and conversely will move furhcr apart in case of decelera- On the other han', the second impulse generated byl the passage' of the pir 3 in front of the inclined diagonal rib of the Z will vr "y as a function of of axial displacement, and the second line 17 appearing on the screen 15 will s' :roach one or the other of the end lines, depending, or. the case. Thus, the speed of be deduced from the distance between the rst an! the third lines 17, while the axial displacement of the rotor is deduced from the distance separating the first and second lines.

At a stable speed, adjustment of the scanning permits a suitable .position of the third impulse to be chosen, the distance between this latter and the first being constant in respect 'of time. Y The scale thus chosen enables the axial displce'aientof 'the rotor to be deduced by simply measurdispacemcnt of the second impulse.

*In other words, the endina'V ulses constitute a continuand the centra' impulse indicates the axial turbine wheel.

It will 'be 'noted that the measurement is independent of the evoltuion4 the voltage generated is not taken into consideration. It should also be observed of the turbine and an interto the first two.' 'Ihis-electhrough the .agency the amount of the radial clearance, since Vthe value of` that the choice of an angle of 45 ibr the inclination of the diagonal rib of the Z enbles the measurement of the axial displacement to be replaced by that of the corresponding transverse displacement, without introducingy any factor 'o f proportionality due to the slope of the said inclined rib.

The circuit described above'has the advantage that it necessitates only`the connection of asingle wire on the turbine, and furthermore only on a'xcd portion. The

pre-amplifier stage' installed in close proximity is of very small size. The other apparatus can be located at a dis-` tance, for example in the measuring instrument room.

It will of Course be understood be made to the form of embodiment which has just been described, in particular by the substitution of equivalent technical means, without thereby departing from the scope of the present invention.

What I claim is: 1. In a rotating machine comprising as members ro- `tating with respect to each other. a'rotor and a stator, a device tor indicating the axial position of therotor with respect to the stator which comprises: a first electrode located on the periphery of one ofsaid members and com# prising three branches, two of which are parallel and at an'angle to the transverse rotation planes of the rotor and the third of which is at an angle to these two branches and to the transverse rotation planes ot' the rotor; a second electrode located on the periphery of said other member in a transverse plane crossing said three branches; elements connected to the two electrodes respectively and adapt-cd to complete an electric circuit when said second electrode faces a branch of said tirst electrode; and an inclicating apparatus connected to said electric circuit for that modifications may i indicati-g the instants when the second electrode is opposite a branch of the rst electrode. 'Y

2. A device as set forth in claim 1 in which' said two parallel branches ofA snidf rst electrode are parallel to the axis ofrotatfon vof the rotor and said third branch forms at an angle of 'about 45 with said two parallel branches.

s. A dem: as sa forth in claim 1 in which the elec. trode located on the periphery et the stator is connected to earth through the intermediary of the rotor bearings ehe-:eas te electrode located on the periphery of the stato: is put under tension.

References Cited by the Examiner UNITED STATES PATENTS 1,779,7S3

10/30 Sylvander et al. 324-70 1593.959 2/31 Barr 20G-25 2,575,719` ll/Sl -Hardigg 73-7L4 2,B2S,626 4/58` Snmsel' -.1 3244-70 2,829,3"- 4/58 Doll 34-2C6 X 2,913,662 ll/59 .Hogan 324-7-0 2,937,239 5/60 Garbenet al. 324-83 2,983,141 5/61 Vanator -c 73-162 3,058,339 10/'62 Shapiro 'I3-713 FOREIGN PATENTS 204,503 l/S 6 Australia.

RICHARD C. QUEISSER, Primary-Examiner. ROBERT I.. EVANS, JAMES GILL, Examiners. 

1. IN A ROTATING MACHINE COMPRISING AS MEMBERS ROTATING WITH RESPECT TO EACH OTHER A ROTOR AND A STATOR, A DEVICE FOR INDICATING THE AXIAL POSITION OF THE ROTOR WITH RESPECT TO THE STATOR WHICH COMPRISES: A FIRST ELECTRODE LOCATED ON THE PERIPHERY OF ONE OF SAID MEMBERS AND COMPRISING THREE BRANCHES, TWO OF WHICH ARE PARALLEL AND AT AN ANGLE TO THE TRANSVERSE ROTATION PLANES OF THE ROTOR AND THE THIRD OF WHCIH IS AT AN ANGLE TO THESE TWO BRANCHES AND TO THE TRANSVERSE ROTATION PLANES OF THE ROTOR; A SECOND ELECTRODE LOCATED ON THE PERIPHERY OF SAID OTHER MEMBER IN A TRANSVERSE PLANE CROSSING SAID THREE BRANCHES; ELEMENTS CONNECTED TO THE TWO ELECTRODES RESPECTIVELY AND ADAPTED TO COMPLETE AN ELECTRIC CIRCUIT WHEN SAID SECOND ELECTRODE FACES A BRANCH OF SAID FIRST ELECTRODE; AND AN INDICATING APPARATUS CONNECTED TO SAID ELECTRIC CIRCUIT FOR INDICATING THE INSTANTS WHEN THE SECOND ELECTRODE IS OPPOSITE A BRANCH OF THE FIRST ELECTRODE. 